<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>css-learn</title>
</head>
<style>
	.parent {
		width: 500px;
		border: solid 1px green;
		position: relative;
	}
	.top {
		width: 300px;
		height: 200px;
	}
	.parent>div {
		width: 300px;
		height: 150px;
		margin: 10px 0px;
		background-color: #ccc;
		position: absolute;
	}
	.parent .child2 {
		top: 50px;
		left: 100px;
		background-color: yellow;
		z-index: 2;
	}

	.parent .child3 {
		background-color: red;
		top: 100px;
		left: 200px;
		z-index: 1;
	}


</style>
<body>
	<div class="top"></div>
	<div class="parent">
		<div class="child1">
		
		</div>
		<div class="child2">
			
		</div>
		<div class="child3">
			
		</div>
	</div>
</body>
</html>